Heat Pipe Having Displacement Bodies

ABSTRACT

A heat pipe has a closed conduit which is partially filled with a liquid, an evaporator for converting a portion of the liquid in the conduit into vapor and a condenser for condensing vapor in the conduit. A plurality of displacement bodies are displaceably provided in the liquid. The displacement bodies have a higher compressibility than the conduit and a density of the displacement bodies is greater than a density of the liquid.

The present invention relates to a heat pipe having a closed pipeline which is partially filled with a liquid, having an evaporator for converting part of the liquid in the pipeline to vapor, and having a condenser for condensing vapor in the pipeline.

In the case of conventional heat pipes there is the risk of the liquid contained in the pipeline being able to crystallize, for example when the heat pipe is not in operation. The liquid in the pipeline may expand here, thereby damaging the pipeline. The range of application including storage of such heat pipes is therefore limited to a range which is above the crystallization temperature of the liquid contained in the heat pipe.

For example, a heat pipe which has a flexible pressurized insert for insertion into the evaporator side of the inclined heat pipe is known from DE 197 00 042 A1. The insert is constructed from a thin-walled flexural material which is capable of being compressed and thereby absorbing the expansion pressures which are exerted by the operating fluid of the heat pipe when the operating fluid freezes.

It is an object of the present disclosure to state an improved heat pipe.

This object is achieved by a heat pipe having the features of patent claim 1. Advantageous design embodiments and refinements of the heat pipe are stated in the dependent claims.

A heat pipe, more specifically a heat-pipe type heat exchanger, is stated. The heat pipe has a closed pipeline. In particular, the pipeline is closed in a vapor-tight manner. The pipeline is partially filled with a liquid, the latter being the operating medium which is at times also referred to as the operating fluid. The heat pipe has an evaporator which in particular is coupleable to a heat source so as to convert part of the liquid in the pipeline to vapor. Moreover, the heat pipe has a condenser which in particular is coupleable to a heat sink so as to condense vapor in the pipeline. In this manner, the heat pipe is in particular configured for transmitting heat in a substance-attached manner by means of the operating medium from the heat source to the heat sink.

A plurality of displacement bodies are movably disposed in the pipeline. The displacement bodies are in particular disposed in the liquid. The displacement bodies have a higher compressibility than the pipeline. Moreover, a density of the displacement bodies is higher than a density of the liquid. In particular, the density of the displacement bodies across the entire operating and storage temperature range that is envisaged for the heat pipe is higher than the density of the liquid.

By virtue of the compressibility which is elevated in relation to the pipeline, the displacement bodies are advantageously deformable when variations in volume arise, for example in the case of a phase transformation of the liquid from the liquid to the solid phase. In this manner, the deformation of the displacement bodies may reduce forces which are caused by the variation in volume and which act on the wall of the pipeline, such that the risk of damage to the pipeline is reduced.

By virtue of the density of the displacement bodies which is higher in relation to that of the liquid, the risk of an accumulation of the displacement bodies on the phase boundary between liquid and vapor within the pipeline is particularly minor. In this manner, the risk of displacement bodies being located outside the volume of the liquid, where the effectiveness of the former in terms of reducing the forces acting on the pipeline would be compromised or neutralized, during a solidification process of the liquid is reduced. Moreover, in this manner the risk of the displacement bodies impeding the evaporation procedure, for example by reducing the speed of the vapor by way of interaction between the vapor and the displacement bodies, is particularly minor. The risk of the heat-transmission performance being compromised by the displacement bodies is thus particularly minor. The presence of a plurality of displacement bodies enables a particularly disturbance-free flow of the liquid around the displacement bodies. In particular, the volume of liquid in the pipeline is simply continuous, that is to say that the former is not subdivided into individual and mutually separated sub-regions by the displacement bodies. Moreover, the displacement bodies are readily placeable in the pipeline, even if and when the latter is curved, for example.

In the case of one design embodiment the liquid is water or a liquid based on water. The heat pipe according to the present disclosure advantageously allows the employment of water as an operating medium, even if the heat pipe is exposed to temperatures below the freezing point of water, or the freezing point of the liquid based on water, respectively. The heat-transmission density, in particular in the temperature range below 18° C., is particularly high by virtue of the high specific thermal capacity and the enthalpy of vaporization of water, such that the heat pipe may operate in a particularly efficient manner. The risk of bursting or of damage to the pipeline by the expansion in volume of the water when freezing is particularly minor here.

The heat pipe according to the present disclosure is advantageously employable outdoors having water as the operating medium without any other anti-freeze measures.

In the case of one design embodiment, the displacement bodies each have a first volumetric region in which a gas is trapped. In other words, the first volumetric region is a gas-filled volumetric region. Particularly high compressibility is achievable in particular by the gas-filled first volumetric region. Advantageously, by increasing the pressure of the gas trapped in the first volumetric region, the volume of the displacement bodies is readily reducible in a comparatively potent manner.

In the case of one refinement, the first volumetric region receives a foam-material body. The foam-material body is a body which is formed from a foamed material. The foamed material contains cells in which the gas is trapped. The cell walls of the foamed material here are expediently elastic such that forces are transferrable from the liquid in the pipeline to the gas in the first volumetric region. The gas-filled first volumetric region is implementable in a particularly simple and cost-effective manner by means of the foam-material body.

For example, the foamed material may be a closed-cell foam material, that is to say a foamed material in which the walls between the individual cells are completely closed so as to trap gas. Said foamed material may also be a so-called integral foam. An integral foam has a closed external skin which, particularly in comparison with the cell walls, is thick, and a cell-like core. The density of the integral foam preferably decreases from the external skin toward the inside.

The foamed material of the foam-material body may be, for example, polystyrene, a polyurethane, a foamed silicone, or a naturally foaming starch product. The cell walls of the foamed material may be formed from a material which contains a matrix material and particles which are embedded in the matrix material. The matrix material preferably has a lower density than the particles. A foam-material body having a particularly high density is achievable in this manner.

Alternatively or additionally, the displacement bodies, in the case of one embodiment, additionally to the gas-filled first volumetric region, each have at least one second volumetric region which has a higher density than the first volumetric region. In particular, the second volumetric region is formed by a solid body. In the case of one refinement, the first gas-filled volumetric region at points or throughout encloses the at least one second volumetric region. For example, the second volumetric region or the second volumetric regions, respectively, is or are one or a plurality of all-solid bodies which in particular are at points or throughout enclosed by the foam-material body. For example, the second region or regions, respectively, represent a core or a plurality of cores, respectively, of the respective displacement body. Each second volumetric region may have a regular or an irregular external contour. For example, the second volumetric region is configured as a sphere. Compensation of the buoyant force which is initiated by the volume of gas which is trapped in the first volumetric region is achievable in a particularly simple manner by means of the second volumetric region.

The second volumetric region and/or the particles embedded in the matrix material of the foamed material in the case of one embodiment contain at least one of the following materials or are composed of at least one of the following materials: a mineral material such as quartz, for example, a non-oxidizing metal such as stainless steel or aluminum, for example, zinc-plated iron, a non-ferrous metal, a non-ferrous heavy metal, a copper alloy such as bronze or brass, for example, or lead. By virtue of the comparatively high density of these materials, a particularly high overall density of the displacement bodies is achievable by means of the second volumetric region or by means of the particles, respectively.

In the case of one design embodiment, the second volumetric region is foam-covered with the foamed material; in other words, the core is surrounded with the foamed material during production of the foam-material body. Alternatively, the second volumetric region may be subsequently inserted into the foam-material body. To this end, the foam-material body may have a recess for receiving the second volumetric region. The recess may be embodied to size or undersize. For example, a force-fitting connection between the foam-material body and the second volumetric region may be formed in the case of an undersized recess. Alternatively or additionally, the second volumetric region, in particular in the recess, may be adhesively bonded to the foam-material body. In the case of one refinement, a foaming-capable adhesive such as polystyrene, polyurethane, or silicone is used to this end, wherein the foaming-capable adhesive is present in the completed displacement bodies, in particular in the foamed state. Alternatively or additionally, the second volumetric region on the external face there of retaining anchors which latch when being incorporated into the foam-material body. Displacement bodies of this type are producible in a simple and cost-effective manner.

In the case of one embodiment, the at least one second volumetric region is provided with a sheath which for example is configured as a film or a lacquer. For example, the film may have polyethylene, polypropylene, or polystyrene material, or any other film-extrudable material. In the completed displacement body the sheath is preferably disposed between the second volumetric region and the foam-material body.

In the case of one embodiment, the displacement bodies each have a closed outer sheath which in particular contains an elastic plastics material or is composed thereof. The plastics material may be a duroplastic material or a thermoplastic material, for example. The plastics material is, for example, polyethylene, polypropylene, or polytetrafluoroethylene (PTFE).

In the case of one refinement, particles that have a higher density than the elastic plastics material are embedded in the elastic plastics material. For example, the particles have at least one material which has been mentioned above in the context of the second volumetric region. By way of the sheath the risk of liquid ingression into the displacement body is advantageously reduced. The closed outer sheath may also be provided for trapping the gas in the first volumetric region.

In particular in the case of the displacement bodies having a closed outer sheath, an embodiment in which the foamed material has an open-cell foam material or a hybrid-cell foam material, that is to say one containing open and closed cells, may be expedient. Such foamed materials may be produced in a particularly cost-effective manner. The foam-material body is in the case of one refinement, and optionally in addition to the elastic outer sheath, provided with a sheathing of elastic material. Particularly good sealing of the trapped gas and/or protection of the cells of the foamed material may be achieved in this way.

In the case of one embodiment, a total volume of the displacement bodies is at least 5% of a total volume of the liquid in the closed pipeline; in the case of one refinement, the total volume of the displacement bodies is at least 10% of the total volume of the liquid in the closed pipeline. A volumetric proportion of 10% or more is suitable in particular for heat pipes of which the pipeline has dissimilar cross-sectional areas or cross-sectional shapes at various points, and/or in which surface rough nesses on an internal face of the pipeline have dimensions of 5 micrometers or more. The total volume of the displacement bodies is preferably 50% or less, in particular 25% or less, of the total volume of the liquid. In the case of volumetric proportions of this type of the displacement bodies, the risk of one of the first or damage to the pipeline when the liquid solidifies is particularly minor.

In the case of one embodiment, the closed pipeline is self-contained. This means in particular that the pipeline is the topological equivalent to an embedded toroid in the three-dimensional Euclidean space. In particular, said pipeline has an annular basic shape. In the case of another design embodiment the heat pipe has a plurality of closed pipelines which in the case of one refinement are coupled to a common evaporator unit and/or to a common condenser unit. The pipelines run so as to be mutually parallel, for example. Particularly good heat and substance transmission between the evaporator unit and the condenser unit is achievable in this manner.

In the case of one embodiment, a maximum dimension of each of the displacement bodies is smaller than or equal to 0.75 times a minimum internal cross-sectional dimension of the pipeline. Alternatively or additionally, the maximum dimension of each of the displacement bodies is larger than or equal to 0.25 times the minimum internal cross-sectional dimension of the pipeline. For example, the maximum dimension of each displacement body is approximately ½√{square root over (2)} times the minimum internal cross-sectional dimension of the pipeline. Particularly uniform distribution of the displacement bodies in the liquid is achievable in this manner.

In the case of one embodiment, the heat pipe has a liquid-permeable retention element by means of which the displacement bodies are trapped in a sub-portion of the pipeline. For example, the retention element is a mesh which is inserted into the pipeline, or a cross-sectional constriction of the pipeline. In the case of one design embodiment, the heat pipe has a ball cock which contains the retention element so as to trap the displacement bodies in a liquid-conducting internal part of the ball cock.

Further advantages and advantageous design embodiments and refinements of the heat pipe are derived from the exemplary embodiments which are illustrated hereunder, in conjunction with the figures in which:

FIG. 1A shows a heat pipe according to a first exemplary embodiment, in a schematic longitudinal sectional illustration;

FIG. 1B shows a heat pipe according to a second exemplary embodiment, in a schematic longitudinal sectional illustration;

FIG. 1C shows a heat pipe according to a third exemplary embodiment, in a schematic longitudinal sectional illustration;

FIG. 1D shows a schematic cross-sectional illustration of the heat pipe according to the third exemplary embodiment;

FIG. 1E shows a schematic cross-sectional illustration of a heat pipe according to a variation of the third exemplary embodiment;

FIG. 2A shows a displacement body according to a first exemplary embodiment;

FIG. 2B shows a displacement body according to a second exemplary embodiment;

FIG. 2C shows a fragment of the displacement body according to the exemplary embodiment of FIG. 2A, in an enlarged sectional illustration;

FIGS. 3A-3H show displacement bodies according to further exemplary embodiments;

FIG. 4A shows a schematic cross section through a displacement body at a stage of a first exemplary embodiment of a method for producing said displacement body;

FIG. 4B shows a schematic cross section through a displacement body at a stage of a second exemplary embodiment of a method for producing said displacement body;

FIG. 5 shows a fragment of a heat pipe according to a fourth exemplary embodiment, in a schematic longitudinal sectional illustration; and

FIG. 6 shows a fragment of a heat pipe according to a fifth exemplary embodiment, in a schematic sectional illustration.

The same components or components of the same type and components which have the same effect are provided with the same reference signs in the exemplary embodiments and in the figures. The dimensional ratios between the figures and between the elements illustrated in the figures are not to be understood to be to scale. Rather, individual elements may be illustrated in an exaggeratedly large manner for the sake of better clarity or understanding.

FIG. 1A shows a heat pipe 1 according to a first exemplary embodiment, in a highly schematic longitudinal sectional illustration.

The heat pipe 1 has a self-contained pipeline 10. In the case of the present exemplary embodiment, the pipeline 10 has a constant internal cross section which in particular has a minimum cross-sectional dimension D. In the case of a circular cross-section, for example, the cross-sectional dimension D is the diameter. The external cross section may vary at various points of the pipeline 10.

The pipeline 10 is partially filled with a liquid 20. The liquid 20 represents the operating medium of the heat pipe 1. The liquid 20 is preferably water. A region of the closed pipeline 10 that is not filled with the liquid 20 may be evacuated.

The heat pipe 1 has an evaporator 30 so as to convert part of the liquid 20 in the pipeline 10 to vapor. Moreover, the heat pipe 1 has a condenser 40 so as to condense vapor in the pipeline. The evaporator 30 is expediently disposed so as to be downstream of the condenser 40, following the direction of gravity G. In this manner, the heat pipe 1 is configured so as to receive evaporation heat in the region of the evaporator 30, to transmit said evaporation heat to the condenser 40, and to there release said evaporation heat as condensation heat. In this way, the heat pipe 1 is configured for heat transmission from the evaporator 30 to the condenser 40. In the case of one design embodiment, an electronics module 60 is connected to the evaporator 30 in a heat-transmitting manner, so as to discharge heat from the electronics module 60.

A plurality of displacement bodies 50 are disposed in the pipeline 10. The displacement bodies 50 have a density which is higher than a density of the liquid 20, and are movably disposed in the liquid 20. The displacement bodies 50 have a higher compressibility than the pipeline 10.

In the case of the first exemplary embodiment of FIG. 1A, the heat pipe 1 contains displacement bodies 50 which are of dissimilar sizes and are of dissimilar shapes and are, in particular, irregularly disposed.

FIG. 1B shows a second exemplary embodiment of a heat pipe 1. The heat pipe 1 according to the second exemplary embodiment in principle corresponds to that of the first exemplary embodiment, illustrated in the context of FIG. 1A. As opposed to the latter, however, the pipeline 10 contains displacement bodies 50 which all are of the same shape and size. In this manner, the degree of filling of the displacement bodies 50 that is required for satisfactory protection of the pipeline against bursting when the liquid 20 freezes may be particularly low.

FIG. 1C shows a third exemplary embodiment of a heat pipe 1 which corresponds substantially to the heat pipes according to the first and the second exemplary embodiments. In the case of the present exemplary embodiment, the evaporator 30 has a planar connector plate 35 on which the electronics module 60 is disposed. A connector plate 35 of this type is also suitable for the other exemplary embodiments of the invention.

In the case of the present exemplary embodiment, the connector plate 35 is conjointly extruded with the pipeline 10. Alternatively, said connector plate 35 may also be adhesively bonded, welded, or brazed to the pipeline (cf. the variant of FIG. 1E).

The electronics module 60 is adhesively bonded to the connector plate 35, for example, in particular using a thermally conductive adhesive. Alternatively or additionally, a connection between the electronics module 60 and the connector plate 35 may also be produced by clamping and/or screwing.

In the case of one design embodiment, the electronics module 60 is an electric controller, in particular an electric controller of a motor vehicle. The controller is an engine control unit, for example. In this case, the heat pipe 1 is expediently provided for discharging heat from electronic components of the controller via the pipeline 10 to the condenser 40. Particularly efficient passive cooling of the controller is achievable in this manner. In the case of one variant, the electronics module 60 is a telecommunications system which is operated outdoors in particular.

In the case of one design embodiment, the electronics module 60 is a solar module. The solar module has solar cells, for example, which by way of the reverse side thereof are fastened to the evaporator 30. Cooling of the solar cells and therefore advantageously a particularly high degree of efficiency are thus achievable.

In the case of another design embodiment, the evaporator 30 may be thermally coupled to a mirror trough and be configured to at least partially transmit the thermal energy which by means of the mirror trough is concentrated on the evaporator 30 to the condenser 40. In this case, the operating temperature at the condenser 30, in particular by virtue of isothermal heat transmission, depends on the cooling output of the condenser 40.

In the case of one further design embodiment, the condenser 40 is thermally connected to the heat exchanger of a heat pump. Alternatively, the heat of the condenser 40 may be discharged to the ambient air via heat-exchanger plates.

A total volume of the displacement bodies 50 is between 5% and 25%, in particular between 10% and 20% of a total volume of the liquid 20 in the closed pipeline 10, the limits being included in each case. A maximum dimension d (cf. FIG. 1D, for example) of each of the displacement bodies is in the case of the present exemplary embodiments smaller than or equal to 0.75 times the minimum internal cross-sectional dimension D of the pipeline 10, and greater than or equal to 0.25 times the minimum internal cross-sectional dimension D. In particular, the maximum dimension d of each displacement body is approximately ½√{square root over (2)} times the minimum internal cross-sectional dimension D of the pipeline 10.

Exemplary embodiments of the displacement bodies 50 of the heat pipes 1 are discussed in more detail hereunder.

FIG. 2A shows a first exemplary embodiment of a displacement body 50 in a schematic sectional illustration. FIG. 2C shows a fragment of the displacement body according to the exemplary embodiment of FIG. 2A, in an enlarged sectional illustration.

This displacement body 50 is composed of a gas-filled first volumetric region 510. The first volumetric region is formed from a foam-material body of a closed-cell foamed material. In the case of one variant, an integral foam may have been used as the foamed material of the foam-material body.

The gas—air or nitrogen, for example—is trapped in the closed cells 512 of the closed-cell foamed material. The cells 512 are formed by cell walls 514 of the foamed material. The cell walls 514 are formed by a matrix material 515 in which particles 516 are embedded (cf. FIG. 2C). The particles 516 have a higher density than the matrix material 515.

The matrix material 515 is, for example, polystyrene, a polyurethane, a foamed silicone, or a naturally foaming starch product. The particles 516 are expediently formed from one of the materials mentioned earlier.

FIG. 2B a displacement body 50 according to a second exemplary embodiment, in a schematic sectional illustration.

The displacement body 50, like that according to the first exemplary embodiment, has a first gas-filled volumetric region 510. In order for the gas to be trapped in the first volumetric region 510 and/or in order for the mechanical stability of the displacement body 50 to be increased, the present displacement body has an elastic outer sheath 530 which completely encloses the foam-material body and in this way delimits the first volumetric region 510.

The gas-filled volumetric region 510 may contain a foam-material body as has been described in the context of the first exemplary embodiment. The foamed material of the foam-material body may also in the case of the present displacement body 50 be an open-cell foam material or a hybrid-cell foam material. In the case of one variant of the second exemplary embodiment, the foam-material body is omitted, and the outer sheath 530 is only filled with the gas.

The outer sheath 530 contains an elastic plastics material such as polyethylene, polypropylene, or PTFE, or is composed thereof. In order for a particularly high density to be achieved, the particles 536 may be embedded in the plastics material, wherein the particles 536 have one or a plurality of materials that have already been mentioned earlier for the particles, or are composed thereof.

FIGS. 3A to 3H show displacement bodies 50 according to further exemplary embodiments, in schematic sectional illustrations. These displacement bodies 50 have a first gas-filled volumetric region 510 which is enclosed by an outer sheath 530. The first volumetric regions 510 may each be configured as has been described in the context of the preceding exemplary embodiments.

Additionally, each of the displacement bodies 50 in the case of the exemplary embodiments of FIGS. 3A to 3H has at least one second volumetric region 520 which is formed by a solid body and has a higher density than the first volumetric region 510. The second volumetric region 520 has at least one of the materials which have already been mentioned earlier, or is composed of at least one of these materials.

In the case of the exemplary embodiment of FIG. 3A, the second volumetric region 520 represents a heavy core which is completely enclosed by the foam-material body of the first volumetric region 510. In the case of the exemplary embodiment of FIG. 3B, the heavy core at points is enclosed by the foam-material body of the first volumetric region and at points is adjacent to the outer sheath 530. Here, the second volumetric region 520 is in particular disposed completely within the closed outer sheath 530.

In the case of the exemplary embodiment of FIG. 3C, a plurality of heavy cores, presently three thereof, are embedded so as to be mutually separated in spatial terms as second volumetric regions 520 in the foam-material body of the first volumetric region 510 such that the latter completely encloses each of the second volumetric regions 520.

In the case of the exemplary embodiment of FIG. 3D, the precisely one second volumetric region 520 is integrated in the outer sheath 530. Alternatively, the outer sheath 530 may have a recess 532 which is filled by the second volumetric region 520 such that in particular the outer sheath 530 and the second volumetric region 520 collectively but not individually completely enclose the foam-material body of the first volumetric region 510. In the case of the exemplary embodiment of FIG. 3E the second volumetric region 520 is externally adjacent to the outer sheath 530, that is to say on that side which faces away from the first volumetric region 510. In the case of the displacement body 50 of FIG. 3G, a plurality of second volumetric regions 520 which are mutually spaced apart are integrated in the outer sheath 530 of an individual first volumetric region 510, or fill recesses 532 on the outer sheath 530. In the case of a variant of this exemplary embodiment, the second volumetric regions 520 are externally adjacent to the outer sheath 530.

The displacement body 50 according to the exemplary embodiment of FIG. 3F has a plurality of first volumetric regions 510, presently three thereof, which each are formed by foam-material bodies which are enclosed by an outer sheath 530 and which are grouped around a common heavy core as a second volumetric region 520, preferably so as to be adjacent to the latter. In the case of the exemplary embodiment of FIG. 3H, the displacement body 50 has a plurality of second volumetric regions 520 which are positioned between in each case two first volumetric regions 510.

In the case of this and other embodiments of the invention, the second volumetric regions 520 are preferably all-solid bodies, that is to say that they are not hollow. In the case of the exemplary embodiments described above, the second volumetric regions 520 all are spherical. However, they may also be shaped so as to be ellipsoid, polyhedral, or irregular. For example, the second volumetric regions 520 may be formed by crushed mineral material. In the case of refinements, the solid bodies which form the second volumetric regions 520 are provided with a sheathing which may be formed by a film or a lacquer, for example.

The outer sheaths 530 in the case of the exemplary embodiments of FIGS. 3A to 3D and 3G have a basic shape of a spherical shell. In the case of the exemplary embodiments of FIGS. 3E, 3F, and 3H, the basic shape is ellipsoid. Both shapes are suitable for each exemplary embodiment. An irregular sheathing of the second volumetric region(s) 520 by the first volumetric region 510 is also conceivable.

FIG. 4A shows a schematic cross section through a displacement body according to the exemplary embodiment of the alternatives described in the context of FIG. 3D, at a stage of a first exemplary embodiment of a method for producing said displacement body.

In the case of the method, a foam-material body which is provided with a trough 518 is provided as the first volumetric region 510. An elastic outer sheath 530 delimits the first volumetric region 510. The outer sheath has a recess 532 which overlaps the trough 518 such that an opening of the trough 518 is exposed at points or completely exposed.

Furthermore, a solid body, presently a sphere, is provided as the second volumetric region 520. The shape of the trough 518 corresponds to part of the sphere. The sphere 520 is inserted into the trough 518 such that the former fills the trough 518 of the foam-material body and the recess 532 of the outer sheath 530.

The trough 518 may be embodied for an exact fit or so as to be undersized. For example, in the case of an undersized embodiment, a force-fitting connection between the foam-material body 510 and the sphere 520 may be produced by means of insertion of the sphere 520 into the trough 518. In the case of one variant, the second volumetric region 520 is not of spherical shape, but retention anchors (not illustrated in the figures) which latch to the foam-material body when inserted there into are attached to the surface of said second volumetric region 520.

Prior to the second volumetric region 520 being inserted into the trough 518, an adhesive may be applied in order in particular to achieve a particularly stable mechanical connection between the second volumetric region 520 and the foam-material body and/or the outer sheath 530. The method may comprise foaming of the adhesive.

FIG. 4B shows a schematic cross section through a displacement body 50 at a stage of a second exemplary embodiment of a method for producing said displacement body 50.

As opposed to the first method, the foam-material body 510 presently has no prefabricated trough 518 for incorporating the second volumetric region 520. Rather, the heavy core 520 presently is press-fitted into the foam-material body while the latter is deformed. The displacement body 50 produced makes do without an outer sheath 530, for example. Should an outer sheath 530 be present, the foam-material body is formed with the outer sheath 530, preferably after the heavy core 520 has been press-fitted.

FIG. 5 shows a fragment of a heat pipe 1 according to a fourth exemplary embodiment, in a schematic longitudinal sectional illustration. For example, the heat pipe 1 corresponds substantially to the heat pipe 1 according to the second exemplary embodiment discussed in the context of FIG. 1B.

Deviating from the second exemplary embodiment, two liquid-permeable retention elements 70 are disposed in a positionally fixed manner in the pipeline 10 in the case of the present heat pipe 1. In particular, the retention elements 70 are disposed in that part of the pipeline 10 that is filled with liquid 20. By means of the retention elements 70, the displacement bodies 50 are trapped in a liquid-filled sub-portion 12 of the pipeline 10.

The retention elements 70 are presently formed by metallic meshes. In the case of an alternative design embodiment, the pipeline 10 has constrictions as retention elements 70. The constrictions are expediently dimensioned such that the largest internal cross-sectional dimension thereof is smaller than the smallest longitudinal extent of the displacement bodies 50.

FIG. 6 shows a fragment of a heat pipe 1 according to a fifth exemplary embodiment, in a schematic sectional illustration. The pipeline 1, as is the case in the preceding exemplary embodiment, has liquid-permeable retention elements 70, so as to trap the displacement bodies 50 in a sub-portion 12 of the pipeline. In the case of the present exemplary embodiment, this sub-portion is formed by a ball cock 14 of the pipeline. In particular, the retention elements are connected to the ball cock 14 in a positionally fixed manner. In this manner, the displacement bodies 50 are trapped in a liquid-conducting internal part 12 of the ball cock 14.

The invention is not limited by the descriptions by means of the exemplary embodiments thereto. Rather, the invention comprises each new feature as well as any combination of features, including in particular any combination of features in the exemplary embodiments and patent claims. 

1-14. (canceled)
 15. A heat pipe, comprising: a closed pipeline being partially filled with a liquid; an evaporator for converting part of the liquid in said closed pipeline to vapor; a condenser for condensing the vapor in said closed pipeline; and a plurality of displacement bodies being movably disposed in the liquid, said displacement bodies having a higher compressibility than said closed pipeline and a density of said displacement bodies is higher than a density of the liquid.
 16. The heat pipe according to claim 15, wherein said displacement bodies each have a first volumetric region in which a gas is trapped.
 17. The heat pipe according to claim 16, wherein said first volumetric region contains a foam-material body, said foam-material body having cells in which the gas is trapped.
 18. The heat pipe according to claim 17, wherein said foam-material body is formed from a foamed material which contains a matrix material and particles which are embedded in said matrix material, and wherein said matrix material has a lower density than said particles.
 19. The heat pipe according to claim 16, wherein said displacement bodies each have at least one second volumetric region, said second volumetric region having a higher density than said first volumetric region.
 20. The heat pipe according to claim 19, wherein said first volumetric region at points or throughout encloses said at least one second volumetric region.
 21. The heat pipe according to claim 19, wherein said second volumetric region has at least one material selected from the group consisting of a mineral material, quartz, a non-oxidizing metal, a stainless steel, aluminum, zinc-plated iron, a non-ferrous metal, a non-ferrous heavy metal, a copper alloy, bronze, brass, and lead.
 22. The heat pipe according to claim 15, wherein said displacement bodies each have a closed outer sheath which contains an elastic plastics material.
 23. The heat pipe according to claim 22, wherein said displacement bodies have particles that have a higher density than said elastic plastics material and said particles are embedded in said elastic plastics material.
 24. The heat pipe according to claim 15, wherein a total volume of said displacement bodies is at least 5% of a total volume of the liquid in said closed pipeline.
 25. The heat pipe according to claim 15, wherein said closed pipeline is self-contained.
 26. The heat pipe according to claim 15, wherein a maximum dimension of each of said displacement bodies is smaller than or equal to 0.75 times a minimum internal cross-sectional dimension of said closed pipeline.
 27. The heat pipe according to claim 15, further comprising a liquid-permeable retention element and by means of said liquid-permeable retention element said displacement bodies are trapped in a sub-portion of said closed pipeline.
 28. The heat pipe according to claim 15, wherein the liquid is water or a liquid based on water. 